CBS and Clear Channel Partner on Soledad Antenna Project

A new multiplexed FM antenna on KGTV’s Mt. Soledad site is open for business and radiating. John Rigg, San Diego market Director of Engineering for Clear Channel Communications says that his stations KMYI 94.1 MHz, KIOZ 105.3 MHz, and CBS Radio’s KSCF 103.7 MHz have been on the 4-port system since April 5 of this year.

ERI designed and built the system, an SHPX-10AC-HW center-fed 10-bay half-wave spaced array with approximately 5 dB gain. John says “ERI was chosen because their SHPX series antennas present less weight and wind load than comparable antennas from other manufacturers. Their combiner is more modular and easier to install in tighter places, specifically the attic space above the transmitters.”{mosimage}

Clear Channel and CBS have partnered before on a similar project on the site. KIOZ and KSCF have been combined on an adjacent tower for several years. The main tower owned by McGraw-Hill Broadcasting now hosts the new community antenna. Two site developments motivated the participants to build the antenna: the need for a reduction in RF radiation at ground level due to a new residence to the west of the site, and the steep rise in rent at neighboring towers owned by Midwest Television, KFMB-FM/TV.

They now occupy a position just below the tower top, below the KGTV channel 10 antenna, but sharing the aperture of the KGTV-DT UHF array. John says that they did extensive modeling before construction to assure little interaction between those antennas. In fact, the modeling resulted in the fabrication of antenna mounting brackets out of non-conductive materials.

The quest for the master antenna began after completion of a new home two lots away, adjacent and northwest of the neighboring fire station on Via Casa Alta. Hammett and Edison studied ground level radiation at the home and determined a particular hot spot at a steel column that wasn’t going to go away unless a substantial rearrangement of radiators took place. RFR laws state that any contributor of more than 5% of the maximum permissible exposure (MPE) is equally responsible for mitigating the problem regardless of the contribution percentage. Since KFMB and its tenants KIFM and KYXY were farther away and had just completed their new combining array with low downward radiation values, they were let off the hook. Two other Soledad FM broadcasters using the UCSD-owned tower, KUSS 95.7 MHz, and KLQV 102.9, have had to temporarily decrease power to meet the public RFR guidelines.

In February of 2006, the FM broadcasters on the KGTV and UCSD towers agreed to decrease power temporarily by 25% each. The one exception was Super Class B grandfathered, normally 100 kW, KMYI 94.1 (“Star 94”), which due to a null at the site in question did not have to decrease power at all. KMYI was added to the combiner system to allow the new antenna to be installed on the KGTV main tower removing its weight and wind load contribution to the overall tower loading.

Each of the Clear Channel and CBS stations obtained construction permits in mid-2006. ERI delivered the antenna system in late March this year, and crews were waiting to erect it immediately.

John Rigg reports that their expectations regarding both the increased performance of the antennas and their decreased downward radiation have exceeded expectations. They’ve now got KMYI at 77 kW ERP and he’s happy with the coverage. He says the new antenna is higher and the pattern is cleaner than before, so they need less power now to reach their licensed contours.

For his part, Mike Prasser, San Diego Market Director of Engineering for CBS Radio, appreciates John taking the role as project leader. “He should be commended for how smooth the project went. As for the results of the project, I am extremely pleased.” He’s satisfied that they’ve mitigated the RFR issues and says that he is now working hard to get KSCF broadcasting in HD-radio, which should be up in June.